The preparation of organic microparticles/nanoparticles is well known in the coating industry for providing unique properties for coating applications. Such organic microparticles/nanoparticles can be prepared by either emulsion polymerization in an aqueous medium or by dispersion polymerization in a non-aqueous medium. Techniques of preparing the organic microparticles/nanoparticles are well documented. The essential techniques are incorporated into the preparation process to provide stability of the microparticles/nanoparticles during the polymerization process and functionality on the microparticles/nanoparticles for use in later applications.
German Patent DE2746481 describes a procedure to produce reactive micro-gels from unsaturated polyesters and reactive monomer. As described, an unsaturated polyester was emulsified in water with/without an optional surfactant under constant mixing. The resulting reactive micro-gels had a diameter from 10 to 300 nanometers and reactive hydroxyl or carboxyl groups on the surface. The weight ratio of the unsaturated polyester to monomer was from 1:10 to 10:1 to produce the reactive micro-gels.
U.S. Pat. No. 5,176,959 describes crosslinked polymer microparticles produced by emulsion polymerizing a monomer mixture containing a crosslinking monomer having a plurality of polymerizable sites in the molecule, in an aqueous medium containing a polymeric amide-acid and a neutralizing base as an emulsifier/dispersant. The polymer microparticles were then incorporated in thermosetting coating compositions for rheology control and other purposes.
U.S. Pat. No. 5,565,504 describes an aqueous dispersion of a reactive micro-gel comprising a polymer of at least one allyl ether-containing polyester or polyester urethane. The micro-gels had an average diameter of 10 to 1000 nanometers, and were insoluble but swelled in the usual organic solvents, i.e., alcohols (e.g. methanol, isopropanol), ketones (e.g., acetone, methyl ethyl ketone), esters (e.g., butyl acetate) and aromatic and non-aromatic hydrocarbons (e.g., toluene). The aqueous dispersion of the reactive micro-gel was dried without an additional film-forming agent to form a uniform, transparent and reactive film.
A coating composition containing crosslinked microparticles is also described in US Published Application 2005/0228124. The crosslinked microparticles were formed from (i) a C8 to C20 alkyl ester of (meth)acrylic acid; (ii) a polymerizable ethylenically unsaturated monomer having a polar functional group; and (iii) optionally, a polymerizable ethylenically unsaturated monomer, wherein (i), (ii) and (iii) are different from each other; and the polymer had a glass transition temperature of no more than −10° C.
U.S. Pat. No. 7,091,275 describes an aqueous polymeric composition containing select polymeric nanoparticles. The polymeric nanoparticles contain, as polymerized units, at least one multiethylenically unsaturated monomer and at least one water soluble monomer. The polymeric nanoparticles had a mean diameter in the range of from 1 to 50 nanometers. The aqueous polymeric composition was described as useful for preparing coatings having at least one improved property compared to a coating absent the select polymeric nanoparticles.
U.S. Pat. No. 6,586,097 describes crosslinked microparticles between 10-300 nanometers in size. The crosslinked microparticles were obtained by dispersion polymerization in a non-aqueous medium which is a non-solvent for the formed polymer. The reaction composition comprised at least one monomer A comprising only one ethylenic unsaturation, giving the microparticles self-stabilization during and after polymerization without any addition of stabilizing agent; at least one compound B comprising at least two ethylenic unsaturations; and optionally, at least one compound C comprising only one ethylenic unsaturation and/or at least one compound D which is different from A, B and C and comprising at least one ethylenic unsaturation which can undergo radical-mediated polymerization and at least one second reactive function ƒ1 which is other than an ethylenic unsaturation.
U.S. Pat. No. 6,878,776 describes thermosetting compositions comprising crosslinked polymer microparticles with a size ranging from 10 to 300 nm and carrying at least one reactive functional group which can react with at least one of the reactive components of the thermosetting composition. The microparticles may also carry at least one second reactive functional group which can react with another functional group of the same type carried by another microparticle and/or by a reactive component of the thermosetting composition. The microparticles are at least partially soluble, miscible and/or dispersible in the starting thermosetting composition.
WO 2008/006580 describes a process for preparing organic nanoparticles by the steps of (a) preparing a solution comprising an unsaturated polyester and/or a vinyl ester resin, an initiator and a hydrophobic monomer; (b) emulsifying the solution obtained in step (a) in an aqueous phase; and, thereafter, (c) curing the emulsified solution. European Patent No. 1,484,355 describes a process for preparing polymeric nanoparticles with a mean particle diameter of 1 to 200 nanometers. The process is emulsion free and yields a solid level of polymeric nanoparticles equal to or greater than 30 weight %.
Nanoscale materials, such as carbon black, famed silica, titanium dioxide, and organo-clay, have been produced and used for decades. In order to fully disperse these nanoscale materials in a resin medium, high shear mechanical mixing or chemical exfoliation is typically applied during the dispersion process. U.S. Pat. No. 6,887,931 describes thermosetting inorganic clay nano-dispersions comprising an inorganic clay treated in situ with an intercalation agent and an intercalation facilitating agent. CN 1454931 describes a method to incorporate silicon dioxide into an unsaturated polyester resin. The silicon dioxide was added into the reactor at the beginning or during the polycondensation reaction of making the unsaturated polyester resin. The silicon dioxide can be in powder form, in colloid aqueous solution, in organic solution or in a gel form.